The following six months of data were collected on maintenance cost and the number of machine hours in a factory:

Month Maintenance Cost ($) Machine Hours January 16,900 5,600 February 13,900 4,500 March 10,900 3,800 April 11,450 3,700 May 13,050 4,215 June 16,990 4,980 Select the independent and dependent variables.

Independent Variable Dependent Variable

a. Maintenance cost Machine hours

b. Machine hours Maintenance cost

c. Maintenance cost Month

d. Machine hours Month

e. Month Maintenance cost